A curve that can be obtained from the intersection of a right circular cone and a plane.

When these curves are represented in a plane, they are called

**algebraic curves**, which refers to the locus of points in a plane for which the distances to a point (*focus*) divided by the distances to a line (*directrix*) on this plane is a constant (*eccentricity*).Therefore, a conic section is the set of points *P* on the directrix *d*. The number *k* is called the eccentricity of the conic section.

Algebraic curves, commonly referred to as *conic sections*, are circles, ellipses, parabolas and hyperbolas.

The adjective *conical* describes that which has the shape of a cone: conical surface, conical base, etc.